Smartphones, tablets and other portable electronic devices typically use liquid crystal displays with backlights to enhance visibility of the display. The intensity of the backlight may be adjusted based on ambient conditions to improve visibility of the backlight. The backlight accounts for a substantial portion of the total power consumption of the display. Smartphones and tablets with large displays are appealing to consumers. However, increasing the size of the display to meet this consumer demand increases the current consumption of the display and reduces the battery life of the device.
Content Adaptive Backlight Control (CABC), also known as Dynamic Backlight Control (DBC) or Content Adaptive Backlight (CABL), is a technique used in the past to reduce the power consumption of a backlight in an LCD. One CABC approach linearly stretches the histogram of an image to use the full range of the LCD display while simultaneously reducing the backlight by a corresponding amount. These adjustments are done in a way that does not negatively impact the viewer's perception of the image. This CABC approach reduces power consumption of the backlight while preserving the image quality of the displayed image.
As an example, assume that the highest pixel value in a displayed image is stretched by 11.7% to maximize the light transmittance of the pixel. In this example, all the pixel values in the displayed are increased by 11.7%. The backlight can then be dimmed by a corresponding amount to reduce power consumption.
While histogram-based CABC achieves some reduction in the power consumption of a backlight for an LCD, the current savings is limited by the highest pixel value in the displayed image. If any of the color channels in the displayed image are saturated, there will be little or no savings in current consumption. Accordingly, improved techniques are needed to further reduce power consumption in the backlight for an LCD.